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An ecosystem is a living community of plants and animals which also includes elements of the natural environment. Such as climate and soil. Each element in the system, whether living or natural, depends upon, and influences, others. On a world scale, climate is the main factor which determines the nature and extent of the natural vegetation cover. The map below shows the global distribution of ecosystems:

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Within the tropics, areas covered by tropical rainforests closely coincide with areas experiencing the hot and wet Equatorial climate. These areas are close to the Equator and down the wet eastern sides of the continents, Also largely within the tropics are the areas with a hot desert climate. In these areas there is plenty of sunlight and heat for plant growth, but water is in short supply. In hot deserts there are large areas of bare ground between the plants.; plant roots below the surface are often 20 times or more longer than the height of the plant above the surface, which reflects the desperate need to search underground supplies of water.

In temperate latitudes, temperature becomes a more important factor for controlling the nature of the vegetation cover. With increasing distance from the Equator, lack of warmth and shortness of the growing season restrict plant size and variety.